When searching for biosignatures on exoplanets, scientists have traditionally targeted worlds with liquid surfaces similar to Earth’s. A recent MIT study shows that the basic building blocks of life may also persist in a radically different setting—Venus’s cloud layer, which consists of about 98% sulfuric acid. Using high‑field solution NMR, the team demonstrated that short peptides remain stable for weeks in near‑pure sulfuric acid and spontaneously adopt well‑defined three‑dimensional shapes.
First, researchers examined a range of biomolecules (nucleic acids, lipids, amino acids) in the acid and confirmed their integrity. They then focused on peptides. Because the acid solution contains almost no water, hydrolysis of peptide bonds is essentially halted, allowing the chains to survive. Three peptides were studied: a synthetic seven‑residue peptide HHQ, its longer variant HHQ13, and another seven‑residue peptide K7. In concentrated sulfuric acid each peptide folded into an omega‑shaped loop (Ω‑loop). Sulfuric‑acid molecules act as a scaffold, inserting into the loop’s centre and locking the conformation.
In aqueous solution HHQ forms flat β‑sheets that polymerize into fibrils, but under acidic conditions it adopts a distinct ω‑loop. Such loops naturally occur in proteins, linking β‑sheets or α‑helices and playing roles in folding and molecular recognition. The ability of peptides to retain ordered folds in such a harsh solvent suggests they could perform specific biological functions, providing a plausible chemical basis for life in Venus‑like atmospheres.
The findings prompt a reassessment of habitability criteria. The authors plan to investigate peptide nucleic acid (PNA) stability as both single‑ and double‑stranded molecules in acid, and to test longer peptide chains for ω‑loops or other folded motifs. These efforts could uncover how protein‑like structures arise in extreme environments and guide future Venus missions in the search for novel biosignatures.
Blogger's Review: This work overturns the assumption that strong acids preclude complex chemistry, showing that peptides not only survive but also fold in near‑pure sulfuric acid—an exciting step toward expanding the definition of habitable worlds.